vanishing point is off the page :(

[agrmrs]

hi ,i'm here with a question which relates to perspective drawing

so as u see in below picture i'm trying to make this tower in 2 point perspective , let's say i created the line A for tower base with a specific angle , so it goes far away and meets the eye line also called the vanishing point .so the line B should also meet at the vanishing point.but in this case the vanishing point is probably off the drawing canvas and due to that i'm not able to decide the angle of the line B .so is there any way to measure the angle of the line B correctly when the vanishing point is off the page.coz it comes more difficult when i need to add some windows etc to the tower wall .thank you very much

[Psychotime]

You can't just grow the canvas to fit the spot, then turn it back to normal when you don't need it anymore? Just write down what the intended image size is supposed to be, and crop it back to that size when you're ready.

[LORD M]

If you're using photoshop which I presume you are then bring forth the rulers (shortcut ctrl+R), at the side of the canvas up and left two rulers are now created which you can draw some guide lines from with your mouse. Place these where you think the vanishing point should be, A & B should both use same vanishing point for correct perspective.

[Medelo]

You can also draw out the main perspective lines in your scene in a small thumbnail and then enlarge it to the final size you wish your drawing/painting to be at.

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In Photoshop, I suggest you use paths for horizon line, vanishing points, lines through these, grids, and other construction lines. They provide accuracy at all zooming levels, and you can use them to plot lines in your artwork. Also, they don't increase your canvas and file size.

[OldJake666]

The vanishing point SHOULD be off the canvas, FAR off the canvas. Otherwise it's bound to look far too extreme and unrealistic. If you're working in photoshop, you can easily extend the canvas, if you're working on paper or another physical substrate you can just extend sheets of paper behind what you're working on.

[Jason Ross]

There is. Divide the 2 vertical segments by the same amount then connect the points.
Take the yellow vertical line from line A and line B and divide it by 8 for example and then mark those 8 points. Then divide the vertical segment where lines A and B meet the edge of the paper by 8 as well. Connect those 8 points to each other and you're ready to draw some accurate lines without a huge ruler.

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Those of you who still appreciate the scent of paper and wooden rulers will love the centrolinead, mentioned on Gurney Journey. I had never heard about it, will never use it, but I love it...

[Elwell]

Elaborating on Jason Ross' post, you can determine the spacing of the verticals as well. Continue to divide the side plane by using crossing diagonals, as you've already started to do. Assuming that your initial perspective setup is correct (not always a safe assumption), you can divide any rectangle into an infinitely small grid using diagonals to find the centers. Demonstration here.